Purification of substances by microbial action



Patented Nov. 6, 1951 PURIFICATION OF SUBSTANQES BY MICROBIAL ACTIOH Raymond J. Strawinski, Long Beach, Calif., as-

signor to Texaco Development a Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application July 1, 1948, Serial No. 36,441

4 Claims.

This invention relates to the purification of substances including hydrocarbons and the like, and more particularly to the removal of sulfurbearing complexes or complex sulfur compounds from petroleum hydrocarbons.

,Crude oil, in some cases, is characterized by the presence of objectionable quantities of sulfur compounds, mostly in complex form, which must be removed or substantially reduced in amount, dependent on the use of the final products, to eliminate possible corrosion by such final products when put in use. Such sulfur compounds are further objectionable in such final products as fuels for internal combustion engines in that they may tend to reduce the efliciency of antiknock compounds such as tetraethyl lead, and may, when used alone, reduce the octane number of the fuel. Such crudes cannot be handled by conventional refining methods because of the corrosive effect of the sulfur compounds. Modification of the usual refining processes plus additional steps are required in the refining of such crudes to either abstract the sulfur compounds or reduce them to unobjectionable amounts. require expensive and special apparatus, involve corrosion problems, and add materially to the cost of the final products.

While it is known that certain microorganisms will attack complex sulfur compounds, the action 01' such microorganisms is generally very slow and becomes slower as the extent of metabolism proceeds because of the accumulation of the products of metabolism which may be used in further metabolism by the microorganisms and therefore divert them from the originally desired activity.

To illustrate certain species of Pseudomonas bac-' teria and other microorganisms may metabolize the sulfur complexes in a petroleum hydrocarbon to sulfates which may then be used by them to attack hydrocarbons instead of the organic sulfur complexes. This will slow the metabolism to a point whereby the desired metabolism can be said to have reached equilibrium and will be halted. In the case of sulfur removal this is highly 0bjectionable.

One object of this invention is to provide a novel process wherein the removal of so-called impurities from substances by microbial action is promoted.

Another object of this invention is to provide a novel process wherein the metabolism of such impurities as complex sulfur compounds in petroleum hydrocarbons is maintained at a relatively rapid rate, the retarding or diverting effect of a Such process modifications product of the metabolism being substantially eliminated.

Another object of this invention is the provision of a novel process wherein the removal of impurities such as complex sulfur compounds from petroleum hydrocarbons is rendered more complete.

Other objects and advantages of the invention will appear from the following description and claims.

Briefly described, the present invention can be said to involve the removal as by conversion or metabolism of a relatively complex so-called impurity from a substance such as crude oil or hydrocarbon fractions by the action of selected microorganisms which act upon the impurity to form certain products of metabolism; and the action of different selected microorganisms which act upon the products of metabolism of the first microorganisms and convert such products to readily removable or separable products. More specifically, the invention involves the metabolism or conversion in petroleum hydrocarbons of complex sulfur compounds to sulfates by the action of certain specific microorganisms, and the reduction of the sulfates to easily removed products such as hydrogen sulfideby sulfate-reducing microorganisms.

As an illustration of an application of the invention, bacteria such as certain species of Pseudomonas, Alcaligenes, Bacillus or other genera or any microorganisms which are capable of converting the sulfur-bearing complexes in a petroleum hydrocarbon to sulfates are grown in a mineral-salt nutrient medium in the presence of a small proportion, about 5 to 20%, of the petroleum hydrocarbon to be treated, and in the substantial absence of inorganic sulfur. Such min-, eral salt mediums or nutrient solutions are wellknown to the art, one example being formed of 1000 ml. of distilled water having the following mineral content:

Grams NaH2PO4H2O 1 Kai-IP04 2 NH4NO3 2 MgClzfiHzO 0.25 MllCl24H2O 0.0 1 CaCOa 0.0 1 FeCl2 0.01

The medium may be further altered by the addition of pure accessory growth substances, i. e., vitamin and/or amino acids to promote growth of any desirable microorganism. The pH is preferably adjusted so that after sterilization, it is about 7. The addition of certain ions such as copper, mercury, zinc, bismuth and iodine to the medium in trace amounts may stimulate the activity of the microorganisms. Care must be exercised in the amount added since whensuch ions are present in more than trace amounts, they tend to poison the microorganism.

Sulfate-reducing microorganisms such as bacteria of the anaerobic type (Vibrio desulfuricans, Vibrio estuarii, Vibrio thermodesulfuricans, or Desulfovibrio being mentioned by way of example) are grown in another lot of a, medium such as the following:

K2HPO4 g 0.5 NHiCL g 1 MgSO4HI-I2O g 2 CaSO4.2HaO g 1 Nit-2804 g 1 ICaClzZI-IzO g 0.1 Crude oil g 3.5 Mohrs salt (ferrous ammonium sulfate) Trace H2O ml 1000 Incubation is under anaerobic conditions. After good growth is obtained, the culture is centrifuged and washed with 0.85% sterile saline solution to remove excess sulfate.

The crude oil or hydrocarbon fraction to be processed is then inoculated with the two cultures, the sulfate reducer preferably being added after sulfate has become available from the organism attacking the sulfur complex.

The conditions maintained are such as to encourage both metabolisms, i. e., the action of both sets of microorganisms. Preferably, the conditions are such that the temperature is maintained within a range of 25 to 30 C. and the pH within a range of 6.5 to 7.5. In their action upon the hydrocarbon, the Pseudomonas.

or other organism selected as the sulfate producer functions to assimilate the sulfur-bearing complexes, the resultant end-product being sulfate with a small proportion of some water-soluble organic intermediate compounds. Whereas the sulfate would immediately operate to slow down or divert the action of the Pseudomonas and in time might halt its organic sulfur conversion completely, the sulfate-reducing microorganism operates immediately to reduce substantially all the sulfate to hydrogen sulfide which may be readily removed. Thus the Pseudomonas immediately produces more sulfate from the sulfur complex in the hydrocarbon, thereby effecting the destruction of more of the sulfur complex. The net effect is the continued removal of one of the products of the initial decomposition whereby the reaction proceeds to completion.

By delaying the inoculation with the sulfatereducer until the first organism, i. e. the sulfateproducer has grown to some extent, the growth of the latter will reduce the oxidation-reduction potential in addition to producing sulfate so that the sulfate-reducer will encounter an environment more suited to its growth. Ammonium nitrate can be made available to satisfy the ammonium-nitrogen necessary for the growth of the sulfate-reducer, the nitrate-nitrogen also being available for the sulfate-producer which may also secure its oxygen therefrom. If the sulfate-producer is of a specie that cannot use oxygen in this form, citrate, lactate and equivalen'ts can be used where atmospheric oxygen is not available.

If the specific sulfate producing organism will not lower or maintain the necessary oxidationreduction potential for the anerobe, then a method of electrolytically controlling the potential can be used. A typical method is disclosed in a report in Archives of Biochemistry 2 183 (1943) by Martin E. Hanke and Gale J. Katz entitled "An Electrolytic Method for Controlling Oxidation-Reduction Potential and Its Application In The Study of Anaerobiosis." Under these conditions the reaction can be carried out in a stream of air.

If desired, the hydrogen sulfide produced by the sulfate-reducer may be removed as soon as formed by passing a relatively inert gas through the liquid. The gas can be cleaned subsequently of the hydrogen sulfide and recycled.

While some hydrocarbon may be converted by the microorganisms in the conversion of the sulfur complexes and the sulfates, the amount of hydrocarbon lost in this manner can be considered negligible.

The principle of the invention may be applicable to processes other than the desulfurizing of hydrocarbons which has been discussed only by way of example. The process of the invention is applicable to any like processing wherein the products of the first metabolism are susceptible of conversion by a second microorganism or group of microorganisms to readily removable products.

It will be noted that throughout the process described, the desired specific action can proceed for a longer period of time, resulting in more complete action, and that the action of the first microorganisms, the sulfate-producer, is such as to produce and maintain the most favorable conditions for the second microorganisms, the sulfate-reducers.

The term microorganisms as used herein is intended to include bacteria, their enzymes and other products as well as related fungi and molds.

Obviously many modifications and variations of the invention as above setforth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A method for converting or metabolizing relatively complex sulfur compounds in petroleum hydrocarbons to readily removable products by microbial action comprising the steps of subjecting hydrocarbons under metabolizing conditions to the action of bacteria selected from the class consisting of species of Pseudomonas, Alcaligenes and Bacillus, and subjecting the products of the metabolism to the action of sulfate-reducin bacteria selected from the class consisting of species of Vibrio desu lfuriwns, Vibrio estaurii, Vibrio thermodesulfuricans and Desulfovibrio.

2. The method of claim 1 wherein said first mentioned bacteria are grown in a mineral-salt medium containing a small proportion of the hydrocarbon to be'treated and in the substantial absence of inorganic sulfur prior to charging the bacteria to the main portion of hydrocarbon to be treated.

3. The method of claim 1 wherein said firstmentioned bacteria are grown in a mineral-salt medium containing about 5 to 20% of the hydrocarbon to be treated and in the substantial absence of inorganic sulfur prior to chargin the bacteria to the main portion of the hydrocarbon to be treated.

4. A method for converting or metabolizing relatively complex sulfur compounds in petroleum hydrocarbons to readily removable products by microbial action comprising the steps of subjecting hydrocarbons under metabolizing con- 5 ditions including a temperature in the range of 25 to 30 C. and a. pH in the range of 6.5 to 7.5 to the action of bacteria selected from the class consisting of species of Pseudomonas, Alcaligenes and Bacillus, and subjecting the products of the metabolism to the action of sulfate-reducin bacteria selected from the class consisting of species of Vibrio desulfuricans, Vibrio estuarii, Vibrio thermodesulfuricans and Desulfovibrio.

RAYMOND J. STRAWINSKI.

REFERENCES crrEn UNITED STATES PATENTS Number Name Date 1,685,004 Mislin Sept. 18, 1928 1,753,641 Beckman Apr. 8, 1930 2,056,668 Bavin Oct. 6, 1936 2,291,009 Underkofller July 28, 1942 2,356,218 Christensen Aug. 22, 1944 2,413,278 Zobell Dec. 24, 1946 OTHER REFERENCES mausmn Microbiology, by Smyth & Obold, 1930 ed., page 244. 

1. A METHOD FOR CONVERTING OR METABOILIZING RELATIVELY COMPLEX SULFUR COMPOUNDS IN PETROLEUM HYDROCARBONS TO READILY REMOVABLE PRODUCTS BY MICROBIAL ACTION COMPRISING THE STEPS OF SUBJECTING HYDROCARBONS UNDER METABOILIZING CONDITIONS TO THE ACTION OF BACTERIA SELECTED FROM THE CLASS CONSISTING OF SPECIES OF PSEUDOMONAS, ALCALIGENES AND BACILLUS, AND SUBJECTING THE PRODUCTS OF THE METABOLISM TO THE ACTION OF SULFATE-REDUCING BACTERIA SELECTED FROM THE CLASS CONSISTING OF SPECIES OF VIBRIO DESULFURICANS, VIBRIO ESTAURII, VIBRIO THERMODESULFURICANS AND DESULFOVIBRIO. 